Apparatus for making reflector surfaces



Dec. 30, 1952 G. W. ONKSEN, JR, ET AL APPARATUS FOR MAKING REFLECTORSURFACES Filed Sept. so, 1948 Zil WM y (liter; QL

Patented Dec. 30, 1952 APPARATUS FOR MAKING REFLECTOR SURFACES George W.Onksen, Jr., Anderson, Arthur H. Stuart, McCordsville, and Grove S. Dow,Jr., Anderson, Ind., assignors to General Motors Corporation, Detroit,Mich., a. corporation of Delaware Application September 30, 1948, SerialNo. 52,912

11 Claims. 1

The present invention relates generally to means for forming planesurfaces on elements and more particularly to a fixture adapted toreceive a plurality of die forming elements for the simultaneous formingof plane surfaces on each of the elements by a grinding and lappingoperation.

In the reflector art there are a number of geometric configurationswhich when incorporated in the surface of a glass blank form anefficient light reflecting surface. A configuration commonly employed insuch surfaces is that of the cube corner comprising the three trihedralrhombic surfaces. With a multiplicity of cube corners impressed in thesurface of a glass or plastic material so that the, plane surfaces areat right angles to each other, a reflecting surface is formed which isextensively used in vehicle reflectors. Such a reflector is illustratedin Patent 2,086,356 granted to Falge et al., July 6, 1937.

In constructing the die matrix for the molding of multi-surfaced cubecornered glass and plastic reflectors it has been a common practice toform the die of a plurality of elements of hexagonal cross section, themolding ends of which have been shaped usually by grinding and asubsequent lapping operation to provide a plurality of contiguous planesurfaces each being in extremely accurate angular relationship not onlywith each other but with the locating faces of the elements as well. Asa considerable number of elements are employed in the forming of the diematrix, it is desirable to employ means which are adapted to accuratelyshape the ends of a large number of elements simultaneously. Heretofore,this has been accomplished by providing a holding fixture for theelements in which a plurality of elements are grouped with a locatingface of each of the peripheral elements in engagement with the fixture.A fixture providing such an arrangement of elements for grinding andlapping of the molding surfaces is not entirely satisfactory as errorsin alignment of the elements centrally located in the group are apt tobe introduced when the elements are rotated for the forming of acontiguous surface. Such errors may result from the adherence ofparticles of the surfacing materials-to the locating faces of theelements even though extreme care is exercised in the cleaning of thefixture and elements between subsequent surfacing operation. Such errorsalso may be introduced by elements with improperly aligned loeatingfaces. In the grouping or clustering of elements for the surfacingoperation such errors may become cumulative toward the center of thegroup resulting in the rejection of considerable numbers of the elementsas unsatisfactory for the die matrix.

It is therefore an object of the present invention to provide improvedmeans for supporting a plurality of dieforming elements for accuratelyforming the molding surfaces thereon.

Itis another object to provide an improved means for supporting aplurality of die forming elements for forming the molding surfacesthereon whereby at least one locating face of each element is inengagement with the supporting means.

These and other objects are attained in accordance with the presentinvention by providing a holding fixture having a plurality of spacedparallel pockets, each pocket being adapted to hold a plurality of dieforming elements .in a row with adjacent elements in staggeredrelationship and at least one of the locating faces of each element inengagement with the side walls of the fixture.

For a better understanding of my invention, reference may be had to theaccompanying drawing in which:

Figure 1 is an enlarged fragmentary view in perspective of a holdingfixture embodying the present invention. Figure 2 is a side view takenalong the line 2-2 of Figure 1. Figure 3 is an enlarged fragmentary viewtaken along the line 3-3 of Figure 2 and Figure 4 is an enlarged viewillustrating the angular position of the staggered elements in theholding fixture.

Referring now to the drawing and particularly to Figures 1 and 2 thereis illustrated a flxture embodying the present invention which isadaptedto hold a plurality of elements of hexagonal cross section toformequiangular trihedral surfaces thereon by a grinding and lappingoperation.

The fixture comprises a supporting base 2 upon which thereare detachablymounted a side positioning member 4, a pair of guide and clampingmembers 6 and a plurality of element spacing members 8. The supportingbase 2 is in the form of a rectangular plate of considerable mass withparallel plane surfaces It and I2 which are pref erably treated toresist wear. The guide and clamping members arein the formof generallyrectangular solid blocks with one side undercut to form a right anglerecess 14 extending lengthwise of the members. They are positionedon'the base adjacent its ends with the undercut sidesppipositelydisposed and are held in position by a pair of dowel pins it whichcooperate with cylindrical recesses l8 and 20 respectively locatedadjacent the marginal edges of the guide members 6 and the supportingbase 2. The guide members 6 are clamped in position on the supportingbase by threaded screws 22. The positioning member is in the form of arectangular bar and is disposed lengthwise of the support in abuttingrelationship with the end faces of the oppositely disposed guide members6. The positioning member 4 is held in abutting relationship with theguide member 6 by dowel pins '24 which cooperate with cylindricalrecesses 26 located adjacent the ends of the positioningmember andcorresponding recesses (not shown) located adjacent the lengthwisemarginal edge of the supporting base 2. The element spacing members 8are substantially similar to each other in form with side faces inparallel planes and with right angle extending sections 28 which areadapted to cooperate with the recess in the guide members '6 to providemeans forpositioning and clamping the spacing members on the supportbase. Each of the spacing members 8 is provided with a groove diagonallydisposed across the spacing member with its side Wall 33 in a planeparallel to the planes of the side faces and its end walls 32 convergingtoward the side wall 30 at an angle of 60 degrees. Adjacent spacingmembers are connected together by threaded screws 34 to define a pocketbetween the adjacent members having the end walls 32, side wall 30 andthe side face of the adjoining spacing member as boundaries. They arealigned on the supporting base 2 between the guide members 6 with thespacing member adjacent the positioning member 4 attached to it by ascrew threaded member (not shown) similar to the threaded member 34.Each of the successively aligned spacing members is thereafter attachedto its contiguous spacing member by the'threaded screws 34.

With afixture such as described a plurality of elements 36 may bedisposed in spaced pockets across the fixture with at least one locatingface of each element in engagement with a side wall of the rigidlymounted spacing members. To position the elements thepositioning member4'and guide members 6 are located onthe supporting base 2 so that theircylindrical recesses coincide with the corresponding cylindricalrecesses in the supporting base'2. The'dowel pins 16 and 24 are theninserted in the coinciding recesses to prevent the positioning member 4and guide members 6 from sliding on the surface I of the supportingbase. A spacing member 8 is then placed between the guide members 6 withits groove adjoining the side face of the positioning member 4. Aplurality of the hexagonal elements 36 are disposed in a row in thepocket formed by the positioning member 4 and the spacing member 8 withadjacent elements in staggered relationship and with their bottom endsin contact with the surface l0 and'at least one locating face of eachelement in engagement with a side wall of the pocket. For positioningthe hexagonal elements in the manner described the width of the groovesin the spacing elements 8 should besubstantially one and onehalf timesthe dimension between parallel faces of the hexagonal elements. Theangle at which the recesses are diagonally disposed across the spacingmembers should be such as to position the elements with'respect to thesupporting base 2 to obtain contiguous plane surfaces which 'are atrightang-les to each other; this being considered rows of elements arepositioned in the same manner with the successively aligned spacingmembers being clamped to each other instead of to the positioning member4. With each spacing member 8 in position on the supporting base 2 theguide members 6 are clamped. to the supporting base 2 by the threadedscrews 22 to rigidly hold the spacing members 8 and elements 36 in aposition on the supporting base.

With the elements rigidly clamped in the fixture the exposed ends aresubjected to a rough grinding operation and thereafter to a lappingoperation including successively finer abrasives to form a highlypolished plane surface. After forming the first surface the clampingscrews are removed and the fixture is disassembled and thoroughlycleaned. It is then reassembled with the elements rotated in the pocketsdegrees for the forming of a contiguous surface. With elements ofhexagonal cross-section the surfacing operation is repeated three timesto form a cube corner comprising three trihedral rhombic surfaces.

The particular advantage of a holding fixture embodying the presentinvention is the manner in which the hexagonal elements are arranged toprovidean engaging contact between the element and the fixture for atleast one locating face of the hexagonal element. With this manner ofarrangement the pins have a rigid and fixed guide surface whichsubstantially eliminates any misalignment of the pins and the subsequentforming of molding surfaces which do not have a proper angularrelationship with the longitudinal axis of the pins and with each other.

While the embodiment of the present invention as herein disclosedconstitutes a preferred form it is to be understood that other formsmight be adopted all coming within the scope of the claims which follow.

What we claim as new and desire to obtain by Letters Patent of theUnited States is:

1. An apparatus for simultaneously forming plane surfaces on the ends ofa plurality ofelements of hexagonalcross section adapted to be assembledin mutual engagement to present a multi-surfaced die matrix comprising asupporting plate having opposite parallel plane supporting surfaces, apair of oppositely disposed guiding and clamping members detachablymounted on one of said surfaces, said guiding members having one faceundercut to provide'in cooperation with said supporting plate guidingand clamping recesses, a positioning member detachably mounted on saidsupporting member with its end portions in abutting relationship withthe ends of said guiding members and a plurality of spacing membersconnectible to each other and as a connected unit of spacers to saidpositioning member between said guiding members, said spacing membershaving reduced end portions extending into said guiding and clampingrecesses and a recess in one side having a side wall parallel with theside of said spacer and converging end walls inclined to the supportingsurface of said supporting plate to provide a plurality of inclinedpockets between adjacent spacing members for clamping a plurality ofsaid elements in a staggered row with each element having at leastonelocating face in engagement with a spacer wall and a locating face ofan adjacent element. l

2. An apparatus for holding a plurality of elements adapted to beassembled in mutual engagement to present a multi-surfaced die matrix,said apparatus comprising a plurality of connectable members, havingoppositely disposed flat side walls, one of said members having aninclined recess in one of said oppositely disposed side walls cooperablewith a flat side wall of an adjacent connectible member to provide aninclined pocket for clamping a plurality of said elements ina staggeredrow and means for securing said members together to clamp said elementsin said pocket. I

3. An apparatus for holding a plurality of elements adapted to beassembled in mutual engagement to present a multi-surfaced die matrix,said apparatus comprising a plurality of connectable members withopposite parallel walls, one of said members having a recess in one wallthereof cooperable with the wall of an adjacent member to provide apocket for clamping a plurality of said elements in a staggered row,said recess having one wall parallel with said parallel walls andconverging end walls disposed at an inclination across said member andmeans for connecting said adjacent members to apply clamping pressure ina plurality of directions to the elements in said row.

4. An apparatus for holding a plurality of elements adapted to beassembled in mutual engagement to present a multi-surfaced die matrix,said apparatus comprising a plurality of connectible members, saidmembers being provided with a recess in one side having a side wallparallel with the side of said members and converging end walls disposedat an inclination across said members to provide a plurality of inclinedpockets between adjacent members for clamping a plurality of saidelements in a staggered row and means for securing adjacent members toapply clamping pressure in a plurality of directions to the elements insaid row.

5. An apparatus for holding a plurality of elements adapted to beassembled in mutual engagement to present a multi-surfaced die matrix,said apparatus comprising a pair of connectible members with oppositeparallel walls, one of said members being provided with an inclinedrecess having one wall parallel with said parallel walls and in one Wallthereof, said recess being cooperable with a wall of the other of saidmembers to form an inclined pocket for clamping a plurality of saidelements in a staggered row and means for securing said members to clampsaid elements in said pocket.

6. An apparatus for holding a plurality of elements adapted to beassembled in mutual engagement to present a multi-surfaced die matrix,said apparatus comprising a support, a positioning member detachablymounted on said support, a plurality of element clamping members mountedon said support and connectable to each other and as a unit of clampingmembers to said positioning member, each of said clamping members havinga recess in one side provided with a side wall parallel with the side ofsaid clamping members and converging end Walls inclined to said supportto provide a plurality of inclined pockets between adjacent connectableclamping and positioning members for clamping a plurality of saidelements in a plurality of staggered rows and means for securing saidconnectable members to clamp said units in said pockets.

'7. An apparatus for holding a plurality of elements adapted to beassembled in mutual engagement to present a multi-surfaced die matrix,said apparatus comprising a support, a pairof oppositely disposedguiding and clamping members detachably mounted on said support, aplurality of connectable spacing members disposed on said supportbetween said guiding and clamping members, said spacing members havingone fiat wall and an oppositely disposed wall having an inclined recesstherein cooperable with the flat wall of an adjacent spacing membertoprovide pockets inclined to said support for clamping a plurality ofsaid elements in a staggered row and means on said guiding and clampingmembers for clamping said spacing members on said support.

8. An apparatus for holding a plurality of elements adapted to beassembled in mutual engagement to present a multi-surfaced die matrix,said apparatus comprising a support, a pair of oppositely disposedguiding and clamping members detachably mounted on said support, aplurality of connectable spacing members disposed on said supportbetween said guiding and clamping members, said spacing members beingprovided with a recess in one side having a side wall parallel with theside of said spacing members and end walls converging toward said sidewall at an angle of 60 and inclined to said support to provide aplurality of inclined pockets between adjacent spacing members forclamping a plurality of said elements in a plurality of staggered rows.

9. An apparatus for holding a plurality of elements adapted to beassembled in mutual engagement to present a multi-surfaced die matrix,said apparatus comprising a support, a pair of oppositely disposedguiding and clamping members detachably mounted on said support, apositioning member detachably mounted on said support to engage saidguiding and clamping members, a plurality of spacing members connectableto each other and as a unit to said positioning member between saidguiding and clamping members, each of said spacing members beingprovided with an inclined fiat sided recess in one wall to form pocketsbetween adjacent spacing members inclined to said support for clamping aplurality of said elements in a staggered row. and means on said guidingand clamping members for clamping said spacing members to said support.

10. An apparatus for holding a plurality of elements adapted to beassembled in mutual engagement to present a multi-surfaced die matrix,said apparatus comprising a support, a pair of oppositely disposedguiding and clamping members detachably mounted on said support, apositioning member detachably mounted on said support to engage saidguiding and clamping members, a plurality of spacing members connectableto each other and as a unit to said positioning member between saidguiding and clamping members, said spacing members being provided with arecess in one side having a side wall parallel with the side of saidspacer and end walls converging toward said side wall at an angle of 60and inclined to the supporting surface of said support to provide aplurality of inclined pockets between adjacent spacing members forclamping a plurality of said elements in a stagame-see 'gered row'andmeanson said guiding and clamping members for clamping saidspacingmembers to said support.

11. An apparatus for holding a plurality 'ofelements of hexagonal crosssection adapted to be assembled in mutual engagement to present amulti-surfaced die matrix comprising a supporting platehaving oppositeparallel planesup'port- 'ing surfaces, a pair of oppositely disposedguiding and clamping members detachably mounted on-one of said'surfaces,a'position'ing member detachably mounted on said supporting member withits end portions in abutting relationship with said guiding members, anda plurality of spacing members connectable to each other and as aconnected unit of spacers to said positioning me-mber'between saidguiding members, each of said spacing members having an inclined recessin one side thereof having a side wall parallel with the side wall ofsaid spacer and converging end walls to provide a plurality of inclinedpockets between adjacent spacing REFERENCES CITED The followingreferences are of record in the file of this patent:

UNITED STATES PATENTS Number Name 7 Date 7 2,056,491 Stimson Oct. 6,1936 2,371,515 "German M21213, 1945 FOREIGN PATENTS Number Country Date'8',082 Great Britain Apr."29, 1892 42,929 Switzerland Jan. '18, 1908

